Don’t allow plants to sit in a tray that has been collecting runoff water. This seedling started “damping off” (dying) due to terrible drainage from bad soil. Seedling is “damping off” due to bad soil with no drainage. Here’s another example of a seedling damping off due to too much water (drowning roots), whis time combined with not enough light.
After a few days of these conditions, this seedling just fell over and started dying. The following plant was grown in an unsuitable growing medium with no drainage and started showing signs of overwatering. Always start with a quality potting mix that has good drainage, and never allow the top of your growing medium to look this wet! The plant roots are drowning from lack of oxygen, causing severe wilting. While oxygen is available to the roots immediately after watering, the roots use up all the oxygen quickly if they are sitting in water. If all the oxygen is gone, roots are not able to get what they need to help power growth, at least not until the growing medium begins to dry out and create new air spaces in the growing medium. Each air spot in the potting mix provides roots with precious oxygen, but if there’s no air spots, roots start to “drown.” By watering seedlings less often, growers can ensure that roots are getting access to plenty of oxygen at all times. Of course you should never allow roots to actually dry out – roots need moisture at all times. But for new growers who want to do everything possible for their new seedlings, it can seem like more water = better. Roots work best when they get as much oxygen as possible while also staying completely moist at all times.
Make sure that the top bit of potting mix has started to dry before you water seedlings again. Sometimes it can take a few days, depending on your growing medium, your environment and how much water you provided during the last watering. Increase the number of air pockets in the growing medium by mixing in a “lighter” amendment like perlite to the potting mix. Perlite will allow the mix to hold onto more oxygen when mixed with heavy soil. Many cannabis soil growers will mix 30-40% perlite into their potting mix to make sure there’s lots of drainage and plenty of air available for the roots. Transplant to a container which allows air in from the sides like fabric pots (“Smart Pots” – highly recommended) or air pots. Start in a smaller container until plant gets bigger so there’s less water in the potting mix that needs to dry. You’ll be able to water your plants more often while ensuring they get plenty of oxygen. Plant processes tend to slow down when temps get cooler. This means that plants usually need water less often than normal after a cold snap. This plant went through a few cool days but the grower continued to water as normal. As a result, the plants roots were surrounded by too much water and the plant started showing signs of overwatering. The plant was watered the right amount each time, but too often. While this won’t kill the plant, the plant will definitely grow faster when the mix is allowed to dry out a bit so the roots are getting plenty of oxygen. Underwatering – seedling is droopy, wilting, or not growing properly, and the growing medium around the seedling isn’t moist. While overwatering is the most common seedling symptom, underwatering is also a problem, especially for those who have been warned to avoid giving too much water. It can be confusing because the symptoms often look similar to each other, which is why it’s important to learn good watering practices. This seedling was underwatered – the grower had been warned many times to avoid overwatering, and went too far in the other direction. It’s crucially important to make sure that plant roots have access to moisture at all times. Plants are constantly losing water through their leaves (called “transpiration”) and this is actually how plants get water up from the roots. As the plants lose water from the leaves, it pulls water up from the ground like a straw. When there’s not enough water at the roots, many plant processes cease to function.
Here’s another example of a young cannabis plant that is underwatered, even in a big container (where the problem is usually overwatering). Notice how this cannabis seedling is basically just wilting and falling over, while the potting mix looks completely dry.
Seedlings suffer greatly from being underwatered, even more so than from overwatering.